JP2000-179326A, published by the Japanese Patent Office in 2000, discloses a regeneration method for a diesel particulate filter (DPF) which traps particulate matter contained in the exhaust gas of a diesel engine. In this method, when the amount of particulate matter trapped in the filter reaches a predetermined amount, the filter temperature is raised to the self-ignition temperature of the particulate matter, whereby the trapped particulate matter is burned and thus the particulate matter is removed from the filter. As a result, the DPF is returned to a state in which particulate matter may be trapped.
The filter temperature is raised by raising the exhaust gas temperature, which is performed by controlling the fuel injection amount and injection timing of the engine. When the temperature of the filter rises to the self-ignition temperature of the particulate matter, the particulate matter burns through self-ignition and is thus removed from the filter.